This proposal describes training in cardiac-cell biology for a PI whose background is in physics and engineering. The training includes 1) graduate courses in cell biology;2) experimental-skill training in molecular and cellular biology;and 3) academic development, including developing a research network and writing manuscripts/proposals. The immediate goal is to improve the Pi's ability to obtain NIH funding, particularly an R01 grant. The long-term goal is to assist the PI in developing his academic career in biomedical engineering with a better balance between his biomedical and engineering proficiencies. To achieve these goals, the PI proposes to investigate the functional differentiation of bone-marrow stem cells in an engineered cardiac myocyte-coculture model. In this model, identical cell-culture microwells will be fabricated to allow creation of a defined stem cell-myocyte interface in each well through application of a laser beam. This model will provide statistically significant data on the regulation of stem-cell differentiation by various types of cocultured myocytes. To test the hypothesis that the microenvironments will regulate the functional differentiation of stem cells into myocytes, the following specific aims will be addressed: 1) Determine the microenvironment's role in regulating stem-cell differentiation into cardiac cells by changing the extracellular matrix, switching the coculture cell types, and genetically modifying the cell-cell juctional protein expressions;2) Use atomic force microscopy to determine the stem cells'mechanical properties by measuring cell stiffness and traction force microscopy to evaluate the cells'mechanical coupling;3) Determine the stem cells'electrical properties by studying action potentials using the patch clamp technique and evaluating electrical coupling using microelectrode arrays. Heart disease is America's leading cause of death for both men and women, accounting for nearly 40% of all annual deaths. By adding to our knowledge of the functional differentiation of bone-marrow stem cells into heart muscle cells, the Pi's research will contibute to the current effort in regenerative medicine to restore the the function of a damaged heart using the patient's own cells. The Pi's institution will provide more than 2,500 sq feet of lab space and unlimited access to all core facilities, which are staffed and provided with state-of-the-art equipment, in addition to 75% release time.